Disazo dyes and inks containing them

ABSTRACT

A compound of Formula (1) and salts thereof                    
     are useful as dyes for ink jet printing inks. In Formula (I) m is 1, 2 or 3; R 1  and R 2  are each independently optionally substituted alkoxy; and R 4  and R 5  are each independently H, optionally substituted alkyl or optionally substituted aryl; provided that at least one of R 1  and R 2  carries an —OH group.

This application is the National Phase of International ApplicationPCT/GB00/00061 filed Jan. 11, 2000 which designated the U.S. and thatInternational Application was published under PCT Article 21(2) inEnglish.

This invention relates to compounds suitable for use as dyes, to inksand to their use in ink jet printing (“IJP”). IJP is a non-impactprinting technique in which droplets of ink are ejected through a finenozzle onto a substrate without bringing the nozzle into contact withthe substrate.

There are many demanding performance requirements for dyes and inks usedin IJP. For example they desirably provide sharp, non-feathered imageshaving good water-fastness, light-fastness and optical density. The inksare often required to dry quickly when applied to a substrate to preventsmudging, but they should not form a crust over the tip of an ink jetnozzle because this will stop the printer from working. The inks shouldalso be stable to storage over time without decomposing or forming aprecipitate which could block the fine nozzle.

According to the present invention there is provided a compound ofFormula (1) and salts thereof:

wherein:

m is 1, 2 or 3;

R¹ and R² are each independently optionally substituted alkoxy; and

R⁴ and R⁵ are each independently H, optionally substituted alkyl oroptionally substituted aryl;

provided that at least one of R¹ and R² carries an —OH group.

Preferably m is 1.

R¹ and R² are preferably each independently optionally substitutedC₁₋₄-alkoxy, provided that at least one of R¹ and R² carries an —OHgroup. The optional substituents which may be present on R¹, R², R⁴ andR⁵ are preferably selected from —NH₂; halo, especially Cl, Br and F;ester, especially —CO₂—C₁₋₄-alkyl; —O—C₁₋₄-alkyl; —CO₂H; —SO₃H; —OR³;and —SR³; wherein each R³ independently is H or C₁₋₄-alkyl, providedthat at least one of R¹ and R² carries an —OH group.

Preferably both R¹ and R² carry an —OH group.

Preferably R⁴ and R⁵ are each independently H, optionally substitutedC₁₋₄-alkyl or optionally substituted phenyl, more preferably H, orC₁₋₄-alkyl or phenyl carrying 1 or 2 groups selected from carboxy andsulpho. More preferably R⁴ and R⁵ are both H.

In an especially preferred embodiment, m is 1 or 2; one of R¹ and R² is—OC₁₋₄-alkyl-OH and the other is —OC₁₋₄-alkyl or —O—C₁₋₄-alkyl-OH; andR⁴ and R⁵ are H.

The compounds of Formula (1) may be prepared by diazotising a compoundof the Formula (2) to give a diazonium salt and coupling the resultantdiazonium salt with a 1-hydroxy-3-sulpho-7-aminonaphthalene:

wherein R¹, R² and m are as hereinbefore defined.

The hydroxy group(s) on R¹ and/or R² may be protected during thediazotisaton, for example using an acid labile or base labile protectinggroup. The acetoxy protecting group is particularly convenient andinexpensive.

The diazotisation is preferably performed at a temperature below 6° C.,more preferably at a temperature in the range −10° C. to 5° C.Preferably the diazotisation is performed in water, preferably at a pHbelow 7. Dilute mineral acid, e.g. HCl or H₂SO₄, may be used to achievethe desired acidic conditions.

The compound of Formula (2) may be prepared by diazotising a carboxyaniline compound and coupling onto an aniline compound carrying the R¹and R² groups at the 2- and 5-positions respectively.

Preferred salts are alkali metal salts (especially lithium, sodium andpotassium salts), ammonium and substituted ammonium salts and mixturesthereof. Especially preferred salts are sodium, potassium and lithiumsalts, salts with ammonia and volatile amines and mixtures thereof. Thelithium salts have good solubility, forming particularly storage stableinks with low toxicity and a low tendency to block ink jet nozzles.

The compounds may be converted into a desired salt using knowntechniques. For example, an alkali metal salt of a compound may beconverted into the ammonium or substituted ammonia salt by dissolving analkali metal salt of the compound in water, acidifying with a mineralacid and adjusting the pH of the solution to pH 9 to 9.5 with ammonia orthe amine and removing the alkali metal cations by dialysis or by use ofan ion exchange resin.

Examples of amines which may be used to form such salts includemethylamine, dimethylamine, trimethylamine, ethylamine, n-propylamine,iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine,tert-butylamine, piperidine, pyridine, morpholine, allylamine,diethylamine, triethylamine, tetramethylamine and mixtures thereof. Itis not essential that the dyes are completely in the form of theammonium salt or substituted ammonium salt and mixed alkali metal andeither ammonium salt or substituted ammonium salt are effective,especially those in which at least 50% of the cations are ammonium orsubstituted ammonium ions.

Still further salts are those with the counter ions described in U.S.Pat. No. 5,830,265, claim 1, integer (b), which are included herein byreference thereto.

The compounds of Formula (1) may exist in tautomeric forms other thanthose shown in this specification. These tautomers are included withinthe scope of the present claims.

According to a second aspect of the present invention there is providedan ink comprising a compound of Formula (1) or salt thereof and a liquidmedium or a low melting point solid medium.

A preferred ink comprises:

(a) from 0.01 to 30 parts of a compound of the Formula (1) or saltthereof; and

(b) from 70 to 99.99 parts of a liquid medium or a low melting pointsolid medium; wherein all parts are by weight and the number of parts of(a)+(b)=100.

The number of parts of component (a) is preferably from 0.1 to 20, morepreferably from 0.5 to 15, and especially from 1 to 5 parts. The numberof parts of component (b) is preferably from 99.9 to 80, more preferablyfrom 99.5 to 85, especially from 99 to 95 parts.

When the medium is a liquid, preferably component (a) is completelydissolved in component (b). Preferably component (a) has a solubility incomponent (b) at 20° C. of at least 10%. This allows the preparation ofliquid dye concentrates which may be used as an ink or to prepare inksand reduces the chance of the dye precipitating if evaporation of theliquid medium occurs during storage.

Preferred liquid media include water, a mixture of water and an organicsolvent and an organic solvent free from water.

When the liquid medium comprises a mixture of water and an organicsolvent, the weight ratio of water to organic solvent is preferably from99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from95:5 to 80:20.

It is preferred that the organic solvent present in the mixture of waterand organic solvent is a water-miscible organic solvent or a mixture ofsuch solvents. Preferred water-miscible organic solvents includeC₁₋₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol andcyclohexanol; linear amides, preferably dimethylformamide ordimethylacetamide; ketones and ketone-alcohols, preferably acetone,methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscibleethers, preferably tetrahydrofuran and dioxane; diols, preferably diolshaving from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethyleneglycol, propylene glycol, butylene glycol, pentylene glycol, hexyleneglycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferablydiethylene glycol, triethylene glycol, polyethylene glycol andpolypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol;mono-C₁₋₄-alkyl ethers of diols, preferably mono-C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms, especially 2-methoxyethanol,2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol,2-[2-(2-methoxyethoxy)ethoxy]ethanol,2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether;cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclicesters, preferably caprolactone; sulphoxides, preferably dimethylsulphoxide and sulpholane. Preferably the liquid medium comprises waterand 2 or more, especially from 2 to 8, water-soluble organic solvents.

Especially preferred water-soluble organic solvents are cyclic amides,especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone;diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol,diethyleneglycol and triethyleneglycol; and mono- C₁₋₄-alkyl andC₁₋₄-alkyl ethers of diols, more preferably mono- C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms, especially((2-methoxy)-2-ethoxy)-2-ethoxyethanol.

Examples of further suitable ink media comprising a mixture of water andone or more organic solvents are described in U.S. Pat. No. 4,963,189,U.S. Pat. No. 4,703,113, U.S. Pat. No. 4,626,284 and EP 4,251,50A.

When the liquid medium comprises an organic solvent free from water,(i.e. less than 1% water by weight) the solvent preferably has a boilingpoint of from 30° to 200° C., more preferably of from 40° to 150° C.,especially from 50 to 125° C. The organic solvent may bewater-immiscible, water-miscible or a mixture of such solvents.Preferred water-miscible organic solvents are any of the hereinbeforedescribed water-miscible organic solvents and mixtures thereof.Preferred water-immiscible solvents include, for example, aliphatichydrocarbons; esters, preferably ethyl acetate; chlorinatedhydrocarbons, preferably CH₂Cl₂; and ethers, preferably diethyl ether;and mixtures thereof.

When the liquidmedium comprises a water-immiscible organic solvent,preferably a polar solvent is included because this enhances solubilityof the compound in the liquid medium. Examples of polar solvents includeC₁₋₄-alcohols. In view of the foregoing preferences it is especiallypreferred that where the liquid medium is an organic solvent free fromwater it comprises a ketone (especially methyl ethyl ketone) &/or analcohol (especially a C₁₋₄-alkanol, more especially ethanol orpropanol).

The organic solvent free from water may be a single organic solvent or amixture of two or more organic solvents. It is preferred that when themedium is an organic solvent free from water it is a mixture of 2 to 5different organic solvents. This allows a medium to be selected whichgives good control over the drying characteristics and storage stabilityof the ink.

Ink media comprising an organic solvent free from water are particularlyuseful where fast drying times are required and particularly whenprinting onto hydrophobic and non-absorbent substrates, for exampleplastics, metal and glass.

Preferred low melting solid media have a melting point in the range from60° C. to 125° C. Suitable low melting point solids include long chainfatty acids or alcohols, preferably those with C₁₈₋₂₄ chains, andsulphonamides. The compound of Formula (1) may be dissolved in the lowmelting point solid or may be finely dispersed in it.

The compounds of the invention may be used as the sole colorant in inksbecause of their attractive black shade. However, if desired, one maycombine the compounds with one or more further colorants if a slightlydifferent shade is required for a particular end use. The furthercolorants are preferably dyes. When further colorants are included inthe ink these are preferably selected from black, cyan and yellowcolorants and combinations 10 thereof.

Preferred black colorants include C.I.Food Black 2, C.I.Direct Black 19,C.I.Reactive Black 31, PRO-JET Fast Black 2, C.I.Direct Black 195;C.I.Direct Black 168; and black dyes described in patents by Lexmark(e.g. EP 0 539,178 A2, Example 1, 2, 3, 4 and 5), Orient Chemicals (e.g.EP 0 347 803 A2, pages 5-6, azo dyes 3, 4, 5, 6, 7, 8, 12, 13, 14, 15and 16) and Seiko Epson Corporation.

Preferred cyan colorants include C.I.Direct Blue 199; C.I.Acid Blue 9;C.I.Direct Blue 307; C.I.Reactive Blue 71; and C.I.Direct Blue 85.

Preferred yellow colorants include C.I.Direct Yellow 142; C.I.DirectYellow 132; C.I.Direct Yellow 86; C.I.Direct Yellow 85; and C.I.AcidYellow 23.

However, as mentioned above, it is not normally necessary to use furthercolorants in conjunction with the compounds of the present invention.

The ink may also contain additional components conventionally used inink jet printing inks, for example viscosity and surface tensionmodifiers, corrosion inhibitors, biocides, kogation reducing additivesand surfactants which may be ionic or non-ionic

A further aspect of the invention provides a process for printing animage on a substrate comprising applying an ink containing a compound ofFormula (1) to the substrate by means of an ink jet printer.

The ink used in this process is preferably as defined in the secondaspect of the present invention.

The ink jet printer preferably applies the ink to the substrate in theform of droplets which are ejected through a small orifice onto thesubstrate. Preferred ink jet printers are piezoelectric ink jet printersand thermal ink jet printers. In thermal ink jet printers, programmedpulses of heat are applied to the ink in a reservoir by means of aresistor adjacent to the orifice, thereby causing the ink to be ejectedin the form of small droplets directed towards the substrate duringrelative movement between the substrate and the orifice. Inpiezoelectric ink jet printers the oscillation of a small crystal causesejection of the ink from the orifice.

The substrate is preferably paper, plastic, a textile, metal or glass,more preferably paper, an overhead projector slide or a textilematerial, especially paper.

Preferred papers are plain or treated papers which may have an acid,alkaline or neutral character.

Preferred papers are plain or treated papers which may have an acid,alkaline or neutral character. Examples of commercially availabletreated papers include HP Premium Coated Paper (available from HewlettPackard Inc), HP Photopaper (available from Hewlett Packard Inc), StylusPro 720 dpi Coated Paper, Epson Photo Quality Glossy Film (availablefrom Seiko Epson Corp.), Epson Photo Quality Glossy Paper (availablefrom Seiko Epson Corp.), Canon HR 101 High Resolution Paper (availablefrom Canon), Canon GP 201 Glossy Paper (available from Canon), and CanonHG 101 and HG201 High Gloss Film (available from Canon).

A further aspect of the present invention provides a paper, an overheadprojector slide or a textile material printed with an ink, a compound orby means of a printing process as hereinbefore defined.

A still further as aspect of the present invention provides an ink jetprinter cartridge, optionally refillable, containing an ink according tothe second aspect of the present invention.

The compounds and inks of the invention have attractive, neutral blackshades and are particularly well suited for the ink jet printing of textand images. The inks have good storage stability and low tendency toblock the very fine nozzles used in ink jet printers. Furthermore, theresultant images have good optical density, light-fastness, wet-fastnessand resistance to fading in the presence of oxidising air pollutants.

The invention is further illustrated by the following examples in whichall parts and percentages are by weight unless specified otherwise.

EXAMPLE 1 Preparation of

Step 1—Preparation of 1,4-bis-(2-Acetoxyethoxy)hydroquinone

Hydroquinone bis-(2-hydroxyethyl)ether (179 g), acetic acid (100 ml) andacetic anhydride (300 ml) were stirred and heated under refluxovernight. After cooling to room temperature and drowning into water (2l) the product was isolated by filtration, washed with water, dried andrecrystallised from ethanol to give 212 g of product.

Step 2—Preparation of 2-Nitro-1,4-bis-(2-acetoxyethoxy)hydroquinone

The product of step 1 (211.5 g) was dissolved in acetic acid (1800 ml).A mixture of nitric acid (51.9 ml) and acetic acid (200 ml) was thenadded over 20 minutes keeping the temperature below 20° C. Afterstirring at room temperature overnight the solution was drowned intowater (9 l) and the product isolated by filtration, washed with waterand recrystallised from ethanol to give 209 g of product.

Step 3—Preparation of 2,5-di-(2-acetoxyethoxy)aniline

2-Nitro-1,4-bis-(2-acetoxyethoxy)hydroquinone (115 g) was dissolved inethanol at 50° C. and reduced with hydrogen in the presence of palladiumcatalyst (2 g, 5%Pd/C). When uptake of hydrogen ceased the solution wasscreened to remove the catalyst and the filtrates allowed to cool toroom temperature. The crystalline solid was isolated by filtration anddried under vacuum to give 90 g of product.

Step 4—Preparation of4-(4-Carboxyphenyl)azo-2,5-di-(2-acetoxyethoxy)aniline 4-Aminobenzoicacid (8.22 g) was stirred in a mixture of water (300 ml) andhydrochloric acid (20 ml). After cooling below 10° C., sodium nitrite(4.55 g) was added slowly. After stirring for a further hour, excessnitrous acid was destroyed using sulphamic acid.2,5-di-(2-acetoxyethoxy)aniline (17.82 g) was dissolved in acetone (500ml) and added to the above diazonium salt solution. After stirringovernight at room temperature the precipitated product was filtered-off,washed with water and used without further purification.

Step 5—Preparation of Title Product

The product of step 4 was dissolved in water by raising to pH9. Sodiumnitrite (8.28 g) was added and the mixture added to a mixture of water(100 ml) and hydrochloric acid (20 ml). After stirring for 1 hour atroom temperature, excess nitrous acid was destroyed using sulphamic acidto give a diazonium salt solution.

1-Hydroxy-3-sulpho-7-aminonaphthalene (16.2 g) was dissolved in water(300 ml) and the pH raised to 10 by addition of sodium hydroxidesolution (2M). After cooling to below 10° C., sodium carbonate (10 g)was added. The diazonium salt solution prepared described above was thenadded slowly, maintaining the pH at 10.5-11. After stirring for 1 hoursodium hydroxide (120 g) was added and the solution heated to 60-65° C.for 2 hours. The pH was adjusted to 7 and ammonium chloride (15%w/v)added to precipitate the dye which was isolated by filtration at 70° C.The isolated solid was washed with hot ammonium chloride solution(20%w/v) and pulled dry on the filter. After conversion to the free acidthe black dye was re-dissolved in ammonia solution and dialysed to lowconductivity.

The title product in the form of its ammonium, salt was isolated byevaporating the water at 50° C. The title product had a λmax at 572 nm.

EXAMPLE 2 Preparation of

This was prepared by the method described in Example 1 except that instep 4 there was used 5-amino isophthalic acid (10.86 g) in place of4-aminobenzoic acid.

The resultant compound had a λmax at 568 nm.

EXAMPLE 3 Preparation of

The method of Example 1 may be repeated except that in place of4-aminobenzoic acid in step 4 there is used 2-amino terephthalic acid.

EXAMPLES 4 to 11

Inks 1 and 2 were prepared having the following formulations:

Component Parts (by weight) Ink 1: Dye from Example 1 (NH₄ ⁺ salt) 3thiodiglycol 9 2-pyrollidone 9 cyclohexanol 1 water 81 Ink 2: Dye fromExample 2 (Li⁺ salt) 3 thiodiglycol 9 2-pyrollidone 9 cyclohexanol 1water 81

Inks 1 and 2 were loaded into empty cartridges of a Canon 4300 thermalink jet printer and printed onto the substrates indicated in Table Abelow. The optical density (“ROD”) of the resultant prints were measuredusing an X-rite spectrometer and the results also shown in Table A.

TABLE A Example Ink Substrate ROD 4 1 XA 1.32 5 2 XA 1.31 6 1 SPP 1.44 72 SPP 2.08 8 1 HG201 2.38 9 2 HG201 2.33 10 1 GP301 1.99 11 2 GP301 2.02Key: XA = Xerox Acid Paper SPP = Seiko Epson Photo Paper HG201 = CanonHG201 Paper GP301 = Canon GP301 Paper

EXAMPLES 12 to 21 Mixtures

The dye mixtures described in Table B may be prepared in which all partsare by weight and are shown in brackets. CID means C.I.Direct, CIR meansC.I.Reactive and CIA means C.I.Acid.

TABLE B MIXTURES Example 12 13 14 15 16 17 18 19 20 21 Dye from Example1(80) 2(90) 1(60) 2(75) 1(95) 1(92) 2(89) 1(81) 2(60) 2(77) No. CIDYellow 132 (10) (4) (7) CID Yellow 142 (10) (5) CID Yellow 86 (5) (6)CIA Yellow 23 (10) (10) CIA Blue 9 (5) CIA Blue 307 (8) CID Black 168(11) CI Food Black 2 (10) (15) (20) CID Black 19 (30) (15) (20)

Inks

The inks described in Tables I and II may be prepared wherein theDye/Mixture described in the first column is the Dye or mixture made inthe above example of the same number. Numbers quoted in the secondcolumn onwards refer to the number of parts of the relevant ingredientand all parts are by weight. The inks may be applied to paper by thermalor piezo ink jet printing.

The following abbreviations are used in Table I and II:

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methyl pyrollidone

DMK=dimethylketone

IPA=isopropanol

MEOH=methanol

2P=2-pyrollidone

MIBK=methylisobutyl ketone

P12=propane-1,2-diol

BDL=butane-2,3-diol

CET=cetyl ammonium bromide

PHO=Na₂HPO₄ and

TBT=tertiary butanol

TDG=thiodiglycol

TABLE I Dye/ Dye Na Mixture Content Water PG DEG NMP DMK NaOH StearateIPA MEOH 2P MIBK 1 2.0 80 5 6 4 5 2 3.0 90 5 5 0.2 12 10.0 85 3 3 3 5 113 2.1 91 8 1 14 3.1 86 5 0.2 4 5 15 1.1 81 9 0.5 0.5 9 16 2.5 60 4 15 33 6 10 5 4 17 5 65 20 10 18 2.4 75 5 4 5 6 5 19 4.1 80 3 5 2 10 0.3 203.2 65 5 4 6 5 4 6 5 21 5.1 96 4 12 10.8 90 5 5 13 10.0 80 2 6 2 5 1 414 1.8 80 5 15 15 2.6 84 11 5 16 3.3 80 2 10 2 6 17 12.0 90 7 0.3 3 185.4 69 2 20 2 1 3 3 19 6.0 91 4 5

TABLE II Dye/ Dye Mixture Content Water PG DEG NMP CET TBT TDG BDL PHO2P PI2 20 3.0 80 15 0.2 5 2 9.0 90 5 1.2 5 12 1.5 85 5 5 0.15 5.0 0.2 132.5 90 6 4 0.12 14 3.1 82 4 8 0.3 6 15 0.9 85 10 5 0.2 16 8.0 90 5 5 0.317 4.0 70 10 4 1 4 11 18 2.2 75 4 10 3 2 6 19 10.0 91 6 3 1 9.0 76 9 73.0 0.95 5 2 5.0 78 5 11 6 12 5.4 86 7 7 13 2.1 70 5 5 5 0.1 0.2 0.1 50.1 5 14 2.0 90 10 1 2 88 10 2 5 78 5 12 5 1 8 70 2 8 15 5 1 10 80 8 121 10 80 10

What is claimed is:
 1. A compound of Formula (I) and salts thereof:

wherein: m is 2 or 3; R¹ and R² are each independently optionallysubstituted alkoxy; and R⁴ and R⁵ are each independently H, optionallysubstituted alkyl or optionally substituted aryl; provided that at leastone of R¹ and R² carries an —OH group.
 2. A compound according to claim1 wherein R⁴ and R⁵ are H.
 3. A compound according to either claim 1 orclaim 2, wherein R¹ and R² are each independently optionally substitutedC₁₋₄-alkoxy wherein the substituents are selected from —NH₂; halo;ester; —O—C₁₋₄-alkyl; —CO₂H; —SO₃H; —OR³; and —SR³; wherein each R³independently is H or C₁₋₄-alkyl, provided that at least one of R¹ andR² carries an —OH group.
 4. A compound according to either claim 1 orclaim 2 wherein both R¹ and R² carry an —OH group.
 5. A compoundaccording to either claim 1 or claim 2, wherein m is 1 or 2; one of R¹and R² is —OC₁₋₄-alkyl-OH and the other is —OC₁₋₄-alkyl or—O—C₁₋₄-alkyl-OH; and R⁴ and R⁵ are H.
 6. A compound according to claim1 having any one of the following formulae and salts thereof:


7. An ink comprising a compound according to claim 1 and a liquid mediumor a low melting point solid medium.
 8. An ink according to claim 7which further contains a cyan or yellow colorant.
 9. A process forprinting an image on a substrate comprising applying an ink containing acompound according to either claim 1 or claim 2, to the substrate bymeans of an ink jet printer.
 10. A paper, an overhead projector slide ora textile material printed with an ink according to claim 7 or claim 8.11. An ink jet printer cartridge, optionally refillable, containing anink according to claim 7 or
 8. 12. A paper, an overhead projector slideor a textile material printed with a compound according to claim
 1. 13.A paper, an overhead projector slide or a textile material printed bymeans of a process according to claim 9.